The Geomorphology of the Lower Usk Valley

Caerleon lies at the confluence of the River Usk and Afon Lwyd. Since Roman times, there has been considerable movement in the course of both rivers which has had an effect on the zone around the fortress, eroding away some areas of the civil settlement and depositing alluvium in others. In order to understand what happened to the fortress’ civil settlement, it is necessary to understand the history of the rivers. As part of a pan-Wales programme to study Roman roads and vici (the term for civilian settlements outside the walls of auxiliary forts), carried out by the four Welsh Archaeological Trusts with funding from Cadw, the Glamorgan-Gwent Archaeological Trust commissioned the River Basin Dynamics and Hydrology Research Group from the University of Wales, Aberystwyth to carry out a geomorphological study of the area in two stages.

The first stage looked at air photographs and historic maps to chart the development of the rivers over the last 120 years and provide a framework in which to set their earlier development. A walk-over survey identified areas where there was the potential to find deposits that would preserve significant evidence. The second stage involved the sampling of suitable deposits and analysis. This work is still ongoing.

We hope that this programme will enable us to identify exactly where areas of settlement have been lost to the rivers. Also, it will allow the targeting of remote sensing surveys, so that time is not wasted investigating recent alluvial deposits and appropriate methods are used where we suspect that Roman remains may be deeply buried under later river deposits. It may also resolve questions of sea-level change by showing whether the River Usk was tidal at Caerleon in Roman times.